Applications

Engineering

Physical Properties

Tensile Strength

Insulations and wire have characteristics resistance to breaking when pulled longitudinally. Tensile strength is the maximum load (expressed in pounds or newtons) reached in a tensile test divided by the cross section area of the test piece. Tensile testes are performed using standard tensile tester which apply a pulling force to one end of a test sample and a tensional load to the other of sufficient amount to just balance the applied load. Minimum tensile strengths are specified by safety and standards agencies such as Underwriters Laboratories (UL) or American Society for Testing and Materials (ASTM).

Elongation

Insulation and wire also have characteristic extension when pulled longitudinally in a tensile tester. This extension or elongation is usually expressed as a percentage of the original test piece length. Minimum elongation percentages are specified in a similar manner to tensile strength.

Aging

Insulations, over time, usually undergo a change in properties such as tensile strength and elongation. These values usually decline.

In order to accelerate this process, insulations are tested in ovens at specified temperatures and times. UL, ASTM, and others establish the maximum loss of tensile strength and elongation permitted.

Solderability

Metals used as electrical conductors vary in their ability to be joined using metals or meal alloys such as tin/lead. This ability to be soldered also declines over time with some metals such as tin when coating copper. Visual tests and standards exist which measure degrees of acceptable solderability. A more objective method involves use of a meniscograph which measures the forces of attraction due to solderability of a given metal.

Flex Testing

Insulation and conductors have varying degrees of ability to withstand repeated bending without breaking. This ability is also related to construction of the product being tested, the angle of the bending, the weight applied, and cycle time.

Cold Bend

Insulations have varying abilities to withstand immersion in cold temperatures. Key variables in testing this capability are type of material, temperature, time, and performance requirements (if any) such as bending, coiling around a mandrel, etc. Usually safety and test agencies have established requirements.

Flame Testing

One of the key issues for wire and cable products is Fire Hazard Assessment. Among the important considerations in assessing fire hazard are flame spread, including ignition and propagation and visible smoke. In the United States the National Fire Protection Association (NFPA) publishes the National Electric Code (NEC) which established requirements for fire hazards for cables used in public buildings. Other safety agencies such as Underwriters laboratories and Canadian Standards Association also establish fire safety requirements depending upon the intended use of the cable.